Kelly Clarkson appeared on Monday's episode of The Ellen DeGeneres show and aired some dirty laundry for a good cause.

Clarkson participated in a new game called "Celebrity Confessions' in which she had to tell Ellen something she'd never told anyone before. What was in it for Clarkson? $10,000 for her favorite charity.

“I’m almost afraid to tell you this, because I’m a horrible human," Kelly started out. "This is a horrible human story.”

Clarkson went on to share how when she was only 18 and on her second date ever, she went out with a guy who was obsessed with his height. “We get there, and I am super self-deprecating. I think it’s the funniest thing ever. To a point. Then it gets real mean to yourself,” Clarkson said. “He proceeded to talk about his height for a solid hour,” 5'3" Clarkson said of her 5'2" date. “I withstood an hour. Then I went to the bathroom and I left.”

"So, you said you were going to the bathroom then you just snuck out?" Ellen asked.

"I left him just sitting there at a Benigans," Kelly confessed.

Clarkson had the audience rolling with her story, but she obviously felt bad about the incident. “I’m going straight to hell, I’m aware. It’s the worst thing I’ve ever done.”